What is cellular respiration (aerobic respiration)? What are the three stagesof cellular
respiration (aerobic respiration)? What is oxidative phosphorylation? - answer✔- metabolic
process leading to uptake of O2 and release of CO2 producing ATP
- Acetyl-CoA production
- Acetyl-CoA oxidation (citric acid cycle)
- Electron transport chain and oxidative phosphorylation-> re oxidation of the reduced
cofactors is coupled to the synthesis of large amounts of ATP
What is glycolysis? How does it fit into the "three stages of aerobic respiration"? - answer✔-
Glycolysis is the initial stage of cellular respiration, occurring in the cytoplasm
How many ATP, NADH and pyruvate molecules does it produce (from one glucose)? What are
the fates of pyruvate from glycolysis? - answer✔- 2 ATP, 2 NADH, 2 Pyruvate
-
What are the basics of glycolysis? - answer✔- incomplete glucose oxidation
- happens in cytoplasm
- 1 glucose (6-carbon) splits to form 2 molecules of pyruvate(3-carbon)
- no carbon released
- 2 NAD+ reduced to 2 NADH
- 2 ATP produced
What is glycolysis "preparation" phase? What are the five reactions in the prep phase? What
are the substrates, products, enzymes, and special characters for each reaction? What are the
structures of the molecules involved in each reaction? - answer✔- glucose mol converted to
two triose phosphate mol. (glyceraldehyde 3-phosphate, GAP) at the expense of 2 ATP
STEP 1- formation of glucose 6-phosphate-- ATP hydrolysis drives the rxn (couple rxn cost 1
ATP)
- negative charge traps
- intro pyruvate
STEP 2- Isomerization-- make C1 avail for phosphorylation, prepare for cleavage
STEP 3- second phosphorylation-- "commitment step"; cost 1 ATP; fructose 6-phosphate (F-1),
fructose 1,6-biphosphate (6-bisP), phosphofructokinase-1 (PFK-1)
STEP 4- Adol cleavage(actual glycolytic rxn)-- proceeds in forward direction bc rxn products
removed quickly, "pulling" the rxn in the direction of the cleavage; 6-bisP-> dihydroxyacetone
phosphate + glyceraldehyde 3-phosphate
STEP 5- Isomerization-- ketose<-> aldose; triose phosphate isomerase
What is glycolysis "payoff" phase? What are the five reactions in the payoff phase? What are
the substrates, products, enzymes, and special characters for each reaction? What are the
structures of the molecules involved in each reaction? - answer✔
What is substrate-level phosphorylation? (How is it different from oxidative phosphorylation?) -
answer✔
Does the "standard free energy change" (standard delta G) reflect the "real free energy change"
in the cells (delta G)? - answer✔- some steps are pos but the overall standard free energy is neg
- at actual cellular concentrations of intermediates, the free energies of all the steps are either
neg or close to zero (actual delta G)
How can NAD+ be regenerated for glycolysis through lactate and alcohol fermentation? What
are the enzymes involved? - answer✔- reduced NADH is re-oxidized in non-energy-generating
rxn. both regen. NAD+ to allow glycolysis to cont.
What are the chemical logics in glycolysis? - answer✔achieves 3 important things
- energy production (ATP NADH)
- precursor production (3-phosphoglycerate feeds into other pathways)
- breakdown of glucose into pyruvate to feed the TCA cycle
- glucose is split into 2 identical trioses (after isomerization)
- simplifies metabolism, only one set of enzymes needed downstream
- phosphorylation traps intermediates inside the cell, prepare for phosphoryl group transfer in
payoff
- isomerization positions carbonyl (glu to fruc) to make C1 avail for phosphorylation, prepare for
cleavage into 2 triose mols
How do other monosaccharides enter glycolysis? (in general, no detail) - answer✔feeder
pathways
Why metabolic pathways need to be regulated? What are the control points in glycolysis -
answer✔- to control the rate of the respective pathway and whether it is turned on or shut off
- hexokinase
-phosphofructokinase-1
-pyruvate kinase
What is hexokinase? What are isoenzymes (isozymes)? What are the two types of hexokinase
isozymes? How are they different? Is hexokinase inhibited by glucose-6-phosophate in liver? -
answer✔- used to keep glucose in the cell: enzymes introducing PO4 on glucose, using ATP
- hexokinases I-III
- low Km: .1 mM, located in all tissues except liver
- inhibited by glucose 6-phosphate
- glocokinase
- high Km: 10 mM, primarily in liver (pancreas, small intestine, and brain)
- not inhibited by glucose 6-phos
Why we say that phosphofructokinase regulation is complex? How does fructose-2,6-
biosphosphate regulate phosphofructokinase (positive or negative) - answer✔- ATP is required,
ut if high, can also bind to allosteric site and inhibit PFK-1
- this is relived by AMP, which competes with ATP for binding at the allosteric site
- Fructose-2,6-bisphosphate is a positive allosteric regulator of phosphofructokinase-1 (PFK-1),
activating the enzyme. (allosteric activator)
26 - answer✔
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